1. Field of the Invention
The present invention relates to a optical character reading apparatus, particularly to a optical character reading apparatus for reading character, for example, a postal code (zip code) or a mail address, described on a sheet of paper where a background is printed in multi colors.
2. Description of the Related Art
In reading a postal code or a mail address described on a mail, generally, an area in which the postal code or the address is described is determined and the postal code or the address is read according to image information corresponding to the area.
Similarly, in reading a postal code or an address described on a mail where a background is printed in multi colors, positions on a mail on which the postal code or the address is described must accurately be located. A conventional character reading apparatus for reading character described on a mail printed in multi colors has been disclosed in Japanese Unexamined Patent Publication JP-A-4-54578.
According to the conventional character reading apparatus, attention is paid to the fact that the postal code or the address on a mail printed in multi colors such as a direct mail, is generally printed in black or in blue. Further, the position on which the postal code or the address is described is determined based on color distribution on the surface of a mail, especially a distribution of black pixels or blue pixels.
The color distribution on the surface is very complicated in a mail that is printed with a picture or a color photograph constituted by many colors as the background. Therefore, a number of black pixels or blue pixels distributed complicatedly and discretely need to be processed in the conventional character reading apparatus. Hence, an enormous amount of image processing calculation is necessary for accurately determining the position of describing the postal code or the address.
Moreover, according to the conventional character reading apparatus, the position of describing the postal code or the address is determined by utilizing only the color distribution on the surface of a mail based on information in respect of black pixels or blue pixels which constitute the describing color of the postal code or the like. Accordingly, when there are black pixels constituting some letter design or the like as a background in the vicinity of the postal code or the address, it is difficult to differentiate the letter design from the postal code or the address. In such a case a portion of the letter design may be included in the determined area of describing the postal code or the address.